Scaling of Ion Bulk Heating in Magnetic Reconnection Outflows for the High-Alfvén-speed and Low-β Regime in Earth’s Magnetotail
Year: 2024
Type: article
Abstract: We survey 20 reconnection outflow events observed by Magnetospheric MultiScale in the low-β and high-Alfvén-speed regime of the Earth’s magnetotail to investigate the scaling of ion bulk heating produced by reconnection. The range of inflow Alfvén speeds (800–4000 km s−1) and inflow ion β (0.002–1) covered by this study is in a plasma regime that could be applicable to the solar corona and flare environments. We find that the observed ion heating increases with increasing inflow (upstream) Alfvén speed, V A, based on the reconnecting magnetic field and the upstream plasma density. However, ion heating does not increase linearly as a function of available magnetic energy per particle, m i V A 2 . Instead, the heating increases progressively less as m i V A 2 rises. This is in contrast to a previous study using the same data set, which found that electron heating in this high-Alfvén-speed and low-β regime scales linearly with m i V A 2 , with a scaling factor nearly identical to that found for the low-V A and high-β magnetopause. Consequently, the ion-to-electron heating ratio in reconnection exhausts decreases with increasing upstream V A, suggesting that the energy partition between ions and electrons in reconnection exhausts could be a function of the available magnetic energy per particle. Finally, we find that the observed difference in ion and electron heating scaling may be consistent with the predicted effects of a trapping potential in the exhaust, which enhances electron heating, but reduces ion heating.
Source: The Astrophysical Journal
Institutions: Space Sciences Laboratory, University of California, Berkeley, University of Maryland, College Park, Southwest Research Institute, Johns Hopkins University, Johns Hopkins University Applied Physics Laboratory, University of Hawaiʻi at Mānoa, University of Hawaii System, University of Delaware, Goddard Space Flight Center, Princeton University, University of California, Los Angeles
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Awards: Observational Investigations of the Scaling of Ion Heating by Magnetic Reconnection in Earth's Magnetotail, G2750416160, G3205849527, G3768111145, G416554826, COLLISIONLESS MAGNETIC RECONNECTION IS A UNIVERSAL PLASMA PROCESS THAT CONVERTS MAGNETIC ENERGY INTO PARTICLE ENERGY. RECENTLY MMS HAS DISCOVERED A NEW REGION AND A NEW REGIME WHERE RECONNECTION TAKES PLACE NAMELY AT THE INTERFACE BETWEEN COLLIDING RECONNECTION JETS FROM TWO ACTIVE X-LINES INSIDE FLUX ROPE-LIKE STRUCTURES AT THE DAYSIDE MAGNETOPAUSE. OF THE FEW EVENTS THAT HAVE BEEN REPORTED SO FAR AN IMPORTANT COMMON FEATURE IS THAT RECONNECTION APPEARS TO BE IN THE RARELY SEEN MAGNETIC PILEUP REGIME INDICATING STRONGLY DRIVEN RECONNECTION WHERE THE CONVERGING (AND INFLOWING) JET SPEEDS MAY HAVE EXCEEDED THE RATE OF RECONNECTION IN THE INTERFACE CURRENT SHEET. ANOTHER IMPORTANT PROPERTY OF COLLIDING JET EVENTS IS THE OCCURRENCE OF DENSITY DEPLETION (INSTEAD OF DENSITY COMPRESSION) AND OPEN-ENDED FIELD TOPOLOGY ASSOCIATED WITH MAGNETIC FLUX PILEUP INDICATING SIGNIFICANT 3D EFFECTS. THE SCIENTIFIC OBJECTIVES OF THIS PROJECT ARE DIRECTLY ALIGNED WITH TWO OF THE HIGH-LEVEL SCIENCE GOALS IDENTIFIED IN THE HELIOPHYSICS DECADAL SURVEY: GOAL #2 - DETERMINE THE DYNAMICS AND COUPLING OF EARTH'S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS. GOAL #4 - DISCOVER AND CHARACTERIZE FUNDAMENTAL PROCESSES THAT OCCUR BOTH WITHIN THE HELIOSPHERE AND THROUGHOUT THE UNIVERSE., G8344486512, Collaborative Research: GEM--Transition from Ion-Coupled to Electron-Only Reconnection
OpenAlex ID: W4401587158